In a typical transformer or inductor a non-conductive body supports an electrical winding, and conductive pins are embedded in the body. The pins are connected to the winding, and at one of their ends the pins extend from the body to form external connection terminals (e.g., for insertion in and soldering to a printed circuit board).
The pins are typically inserted in the bobbin body by forcing them into undersized pre-formed holes, and the winding is typically connected to a pin by the winding wire being wound around the pin and then pulled laterally away from the pin so as to tension the wire to the point at which it breaks. In order to withstand such an operation, the pin must be sufficiently wide so as not to bend significantly as the wire is pulled away. Conversely, the pins must typically be sufficiently pliable to allow the ends extending from the bobbin body to be bent after insertion into a printed circuit board to ensure retention. Pins which are typically made of material having a symmetrical cross-section (e.g., round or square wire) cannot accommodate the conflicting requirements of being large enough to accommodate the wire-pulling stress, but pliable enough to allow the pins to be bent for retention after insertion.
Stamped terminals having an asymmetrical cross-section may be used to resolve these conflicting requirements, but such stamped terminals typically cost between five and ten times as much as such pins.